A 10-year-old boy who has cancer in his jaw and needs "urgent surgery" has vanished, a High Court judge has said.

The youngster, who has not been identified, is Polish and could be in Poland with his parents, Mr Justice Mostyn said.

Detail of the boy's case emerged today in a ruling by the judge following hearings in the Family Division of the High Court in London.

A doctor has told the judge that the boy will die a "brutal and agonising death" within six months to a year if a tumour is not removed "very soon".

Mr Justice Mostyn said the Polish embassy in London was being alerted.

And he urged the boy's parents to co-operate with doctors.

The judge said there was evidence that the youngster had left his home in England with his mother two weeks ago, and evidence that the boy's father had boarded a ferry bound for France in the last few days.

He said the boy was at risk of "serious harm" and the risk was growing with every day that passed.

Mr Justice Mostyn said he had made an order saying efforts should be made to find the boy.

He said it was possible that the boy, who had lived in England with his parents for two years, was in Poland.

Mr Justice Mostyn said an NHS trust with responsibility for the boy's care had asked him to rule that specialists could perform surgery.

Doctors said the youngster's parents preferred to treat their son with "Chinese medicine".

The judge said the couple had "not engaged" in court proceedings.

Mr Justice Mostyn said he had concluded that surgery was in the boy's best interests - notwithstanding his parents' lack of consent.

"(The boy) is 10 years old. He comes from Poland but has lived here with his parents and siblings for two years," said Mr Justice Mostyn in his ruling.

"He has a very rare aggressive cancer in his right jawbone. Its medical name is a craniofacial osteosarcoma. It is about four inches long and one-and-a-half inches wide.

"The unambiguous medical evidence given to me in writing and orally by a distinguished paediatric oncologist ... is that if it is not removed very soon then in six months to a year (the boy) will die a brutal and agonising death.

"She has spelt this out in remorseless and unflinching detail.

"(The boy) will not slip peacefully away.

"The cancer will likely invade his nerve system affecting basic functions such as speaking, breathing and eating.

"His head will swell up grotesquely.

"His eyes may become closed by swelling.

"A tracheostomy may be needed to allow breathing.

"Above all, the pain will likely be excruciating.

"The matter is critically urgent."

Mr Justice Mostyn added: "(The boy's) parents do not consent to the operation. Neither does (the boy).

"He has written to me to say 'I don't want the operation and there is not 100% (chance) to survive after the operation'."

The judge said the boy's parents preferred to treat him with "Chinese medicine" and indicated that they had spoken to a "practitioner".

"The practitioner has not treated a cancer like this before and his technique is to treat the whole body to seek to promote overall wellness," said Mr Justice Mostyn.

"The evidence before me is that even in China, where the use of Chinese medicine is widespread, surgery is the standard treatment for a cancer of this kind."

He said it was in the boy's best interests to have surgery and granted an application sought by the NHS trust.

Mr Justice Mostyn said he wanted the boy's parents to consider what he had said.

He indicated that a transcript of what the oncologist had said in writing and at a hearing was available for the parents to read.

He added: "I hope that (the boy) and his parents will read very carefully this judgment and the witness statement and transcript of the oral evidence of (the oncologist) and conclude that there really is no alternative to this procedure taking place and in them all fully co-operating with it."

Mr Justice Mostyn said he had "no doubt" that surgery was in the boy's interests.

"I give full weight to the wishes of (the boy) as well as those of his parents," he said.

"It is a strong thing for me, a stranger, to disagree with and override the wishes of (the boy) and his parents.

"But I have absolutely no doubt that (the boy) must be given the chance, a very good chance, of a long and fulfilling life rather than suffering, quite soon, a ghastly, agonising, death."

Mr Justice Mostyn indicated that he had heard submissions from lawyers representing the NHS trust, a local authority and a guardian appointed by the court to represent the boy's interests.

The judge said barrister John McKendrick had represented the NHS trust.

He said attempts to serve documents on the boy's parents had not succeeded.

"It appears that on 6 October (the boy's) father left this country by ferry for France; the suggestion is that (the boy) and his mother left two weeks ago," said the judge.

"Plainly (the boy) is at risk of serious harm, a risk that grows with every day that passes."

He added: "It is possible that (the boy) is now in Poland."

Mr Justice Mostyn did not identify anyone involved in his ruling.

He referred to the boy and his parents only by initials and did not name the NHS trust or the local authority involved.